1. Field of the Invention
The present invention relates to a process for producing a calcium silicate shaped product. More particularly, it relates to a process for producing a calcium silicate shaped product which has low bulk density and excellent refractoriness, heat resistance, mechanical strength and dimensional stability and is suitable as a refractory coat, a heat insulator and a lagging product.
2. Description of the Prior Arts
Calcium silicate shaped products especially products made of xonotlite as a main component usually have heat resistance to a temperature of at least 1,000.degree. C. to be suitable as a lagging product, a heat insulator and a refractory.
In usual, calcium silicate shaped products used for a lagging product, a heat insulator and a refractory should have low thermal conductivity and high mechanical strength. Such calcium silicate shaped products have been produced by reacting a calcareous source such as calcium oxide with a siliceous source such as a diatomaceous earth in the presence of water under heating to obtain an aqueous slurry and press filter-molding the aqueous slurry and drying the molded product or steam-curing and drying the molded product. If the molded product is steam-cured or dried just after the press filter-molding, cracks may be formed in the shaped product by suddenly releasing uneven pressure distribution and strain caused in the press filter-molding.
The inventors have studied the above-mentioned problem and have found that an excellent calcium silicate shaped product having no crack can be prepared in stable by a heat treatment under a specific condition before the steam-curing or drying of the molded product after the press filter-molding of the aqueous slurry.